1. Field of the Invention
The present invention relates generally to testing apparatus, and more particularly to an improved portable testing apparatus which is able to measure or indicate the static coefficient of friction between a representative flooring surface material and a representative shoe sole or heel material.
2. Description of the Prior Art
One of the best-known and most widely utilized testing apparatus for measuring or indicating the static coefficient of friction between a respresentative flooring surface and a representative shoe sole or heel material is the James Tester Machine which was originally developed by S. V. James of the Underwriters' Laboratories, Inc. The James Machine includes an upper, weighted, rod or strut which is disposed and movable within a vertical plane and to the bottom of which is pivotably connected a lower strut. The lower end of the lower strut has secured thereto a representative shoe sole or heel material and the lower strut-shoe material assembly rests upon a representative flooring sample suitably secured upon a horizontally disposed table which is movable relative to the vertically disposed, upper strut.
In using the machine during performance of a test, the floor sample is placed upon the movable table and the upper and lower strut members, along with the representative shoe material, are positionally adjusted so that the shoe material is in contact with the upper surface of the flooring sample, such contact thereafter being maintained as a result of the weight being constantly impressed upon the upper, vertically movable strut, which weight force is transmitted to the lower strut. The table is moved in a direction relative to the vertical strut such that the angle between the pivotable strut and the vertical plane of the upper strut is varied and increased as the table is moved, and it is thus apparent that the vertical component of force transmitted to, and within, the lower strut is constant, as the superimposed weight is constant, however, the horizontal component of the force is variable, depending upon the angle defined between the lower strut and the vertical plane of the upper strut at a particular moment of time.
A suitable recording mechanism, such as for example, a graphical chart and a recording pencil, is utilized to monitor the relative movement of the table, the chart being secured to the latter and movable therewith while the pencil is secured to the vertical strut, and upon the occurrence of slip, which indicates that the static coefficient of friction between the flooring and shoe sample materials has been reached, the weighted vertical shaft, along with the recording pencil, drops downwardly thereby marking a substantially vertical line upon the chart. The chart includes a graduated scale in terms of the tangent of the angle defined between the hinged and vertical struts, and consequently, the static coefficient of friction is readily indicated.
While it is thus apparent that the James Machine is readily operative and admittedly quite useful in determining the static coefficient of friction between various representative flooring and shoe sole or heel materials, several disadvantages are quite apparent in considering the aforenoted device, particularly the fact that the same is capable of being utilized only in conjunction with material samples. In other words, as a particular floor sample, for example, must be mounted upon the movable table of the device, the Machine is not capable of performing such tests upon installed flooring at field locations. In addition, auxiliary means, either manually or automatically controlled, are necessary for operation of the movable table.